The invention relates to a compressed air supply system for a commercial vehicle having a compressed air inlet that can be coupled to a compressor, a filter module coupled to the compressed air inlet via a delivery line, a discharge valve unit coupled to a discharge outlet and the delivery line, and a first valve unit and a second valve unit. The first valve unit serves to control a control inlet of the discharge valve unit and the second valve unit is arranged in a regeneration air path for the regeneration of the filter module. At least one pneumatically closable overflow valve serves to supply a consumer circuit coupled to the compressed air supply unit with compressed air.
The invention further relates to a method for operating a compressed air supply system having a compressed air inlet that can be coupled to a compressor, a filter module coupled to the compressed air inlet via a delivery line, a discharge valve unit coupled to a discharge outlet and the delivery line, and a first valve unit and a second valve unit. The second valve unit is arranged in a regeneration air path for the regeneration of the filter module. In the method, at least one pneumatically closable overflow valve serves to supply a consumer circuit coupled to the compressed air supply unit with compressed air and the first valve unit serves to control a control inlet of the discharge valve unit.
Such compressed air supply systems fulfill numerous functions in commercial vehicles. These include, in particular, the supply of dry, purified compressed air to the braking system and other compressed air consumers, the exercise of a multi-circuit safety valve function to reciprocally safeguard various consumer circuits and to ensure a specific filling order, and the provision of a pressure regulator function. The compressed air used by the compressed air consumers is provided primarily by a compressor, which is generally driven by the internal combustion engine of the commercial vehicle. In many systems, the compressor can be brought into an energy-saving state, either by separating a clutch, which serves to couple the compressor to the internal combustion engine, or by pneumatic actuation of a compressor control inlet, in order to bring the compressor into an idling state.
Besides the delivery operating state of the compressed air supply system, an important further operating state to achieve is the regeneration operating state for the filter unit. For this purpose dry, compressed air is fed from the compressed air reservoirs connected to the compressed air supply systems through the filter module in a direction opposed to the delivery direction. The air flowing through the filter module at least partially absorbs the moisture in the filter module before flowing out into the open via the discharge valve of the compressed air supply system.
WO 96/34785 A1 discloses a compressed air supply system, the consumer circuits of which are supplied by pneumatically closable overflow valves. In this way it is possible, irrespective of the closing or opening pressure of the overflow valves, purposely to intervene in the supply or safeguarding of the consumer circuits and the regeneration process by purposely closing one or more overflow valves.
According to WO 96/34785 A1, the regeneration of the compressed air supply unit is accomplished by the opening of a discharge valve and the selective extraction of compressed air from one or more of the consumer circuits. In order to allow this selective extraction, it is necessary to assign to each of the overflow valves a solenoid valve, which is specifically intended for the purpose of closing the overflow valve as required, resulting in a comparatively high overall equipment cost.
The object of the invention is to provide a compressed air supply unit and a method of operation, which will allow influencing of the filling order at the lowest possible equipment cost.
This object is achieved by a compressed air supply system for a commercial vehicle having a compressed air inlet that can be coupled to a compressor, a filter module coupled to the compressed air inlet via a deliver line, a discharge valve unit coupled to a discharge outlet and the deliver line, a first valve unit and a second valve unit, the first valve unit serving to control a control unit of the discharge valve unit and the second valve unit being arranged in a regeneration air path for the regeneration of the filter module, and at least one pneumatically closable overflow valve, which serves to supply a consumer circuit coupled to the compressed air supply unit with compressed air, wherein the at least one pneumatically closable overflow valve is capable of actuation by the compressed air supply system.
Advantageous embodiments of the invention are described herein.
According to an aspect of the invention, at least one pneumatically closable overflow valve is capable of actuation by the second valve unit. The second valve unit therefore has a dual function. On the one hand, it serves to close or open the regeneration air path, the second valve unit itself being an integral part of the regeneration air path. On the other hand, the second valve unit serves for the selective closing of overflow valves, so that a plurality of largely independent functions are advantageously integrated into one component of the compressed air supply unit.
At least one pneumatically closable overflow valve is here usefully assigned to a consumer circuit, which failing pneumatic closure of the overflow valve can be filled with a higher priority than at least one further parallel consumer circuit, so that on closing of the overflow valve at least one further consumer circuit can be filled before the consumer circuit coupled to at least one pneumatically closable overflow valve. Closing of the overflow valves therefore serves to temporarily defer the filling of specific consumer circuits of intrinsically high filling priority, such as the service brake circuits, for example, and instead to fill a circuit of normally low filling priority.
In this context, the further consumer circuit is usefully assigned to the pneumatic suspension of the commercial vehicle.
The provision of an electronic control module is furthermore particularly advantageous. This may, in particular, be integrated into the compressed air supply system. It is further advantageous if the valve units are solenoid valves.
It is furthermore preferable to assign a pressure sensor, which is integrated into the compressed air supply system and is connected to the electronic control module, to the further consumer circuit. It is also feasible, however, for the electronic control module to have an interface, via which signals characteristic of the pressure in the further consumer circuit can be transmitted.
With respect to the method of the invention, at least one pneumatically closable overflow valve is actuated by the second valve unit. In this way, the advantages and particular features of the inventive compressed air supply system are also embodied as a method. This also applies to the especially preferred embodiments of the method specified below.
In a useful development of the method, at least one pneumatically closable overflow valve is assigned to a consumer circuit, which failing pneumatic closure of the overflow valve can be filled with a higher priority than at least one further parallel consumer circuit, so that on closing of the overflow valve at least one further consumer circuit can be filled before the consumer circuit coupled to at least one pneumatically closable overflow valve. The further consumer circuit is furthermore assigned to the pneumatic suspension of the commercial vehicle.
The method is furthermore advantageous in that it is controlled by an electronic control module. The pressure in the further consumer circuit is furthermore usefully determined within the compressed air supply system and in the form of a corresponding signal is transmitted directly to the electronic control module.
Alternatively or in addition, the pressure in the further consumer circuit is determined and in the form of a corresponding signal is relayed to the electronic control module via an interface coupled to a data bus.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.